by Michael S. Kaplan, published on 2005/12/26 15:01 -05:00, original URI: http://blogs.msdn.com/b/michkap/archive/2005/12/26/507402.aspx
Some time ago, Mike asked:
I need to convert some strings to dates and then use the dates for some calculations. I was looking at COleDateTime::ParseDateTime() and it had the statement - "Note that the locale ID will also affect whether the string format is acceptable for conversion to a date/time value." Can you give me some direction on what I need to do? Is there an arcticle(s) I can read to get a handle on this?
A very interesting question.
The COleDateTime::ParseDateTime() method is an interesting one. The remarks in the documentation give a hint as to what is going on:
The lpszDate parameter can take a variety of formats. For example, the following strings contain acceptable date/time formats:
"25 January 1996" "8:30:00" "20:30:00" "January 25, 1996 8:30:00" "8:30:00 Jan. 25, 1996" "1/25/1996 8:30:00" // always specify the full year, // even in a 'short date' formatNote that the locale ID will also affect whether the string format is acceptable for conversion to a date/time value.
It may remind some of the 'Evil date parsing', Parse, and ParseExact post from last year. And with good reason -- it is indeed the evil date parsing logic in COM that is largely responsible for the uncertainty here.
When you attempt to parse a date/time value, the method assumes that the data is valid and will do its best to convert it (using the LCID parameter as a 'hint'), even if the conversion is inappropriate. The method would probably be more stable and generally useful if the LCID were used for more than just a hint about issues like the order of date/month/year versus month/date/year, but at this point the behavior cannot be changed.
So the LCID is just a hint and the hope is that you are passing a date to parse that falls within what is reasonable for that locale....
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# PatriotB on 26 Dec 2005 6:41 PM:
# Michael S. Kaplan on 27 Dec 2005 12:32 AM: